Major Breakthrough On How Viruses Infect Plants

CSIRO plant scientists have shed light on a problem that has puzzled researchers since the first virus was discovered in 1892 — how exactly do they cause disease?

In a major breakthrough that helps us better understand how viruses cause diseases in plants — and potentially in animals and humans — Dr Ming-Bo Wang and Neil Smith of CSIRO Plant Industry have revealed a genetic mechanism that enables viral organisms to infect hosts and cause diseases.

“What we found was that CMV, accompanied by a special type of viral particle called a ‘satellite’, causes its distinctive yellowing symptoms in plants by slicing a gene that makes chlorophyll, the green pigment in leaves. By preventing the production of chlorophyll, the virus causes the leaves to become partially or entirely yellowed which dramatically affects growth and productivity.”

Importantly, Dr Wang and Mr Smith determined the exact gene affected by this virus — a gene called CHL1.

“Pinpointing this gene represents a major step forward in understanding exactly how some viruses cause disease symptoms in susceptible organisms,” Dr Wang said.

Until recently, scientists did not fully understand why viruses only affected a small range of host organisms. This discovery shows that the accompanying satellite gene of CMV must directly match the host plant’s genes to cause the yellowing disease.

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